The present invention relates generally to satellite communication systems, and more particularly, to a multi-step circular horn system for satellite communication systems.
Satellites and other spacecraft are in widespread use for various purposes including scientific research and communications. These scientific and communications missions, however, cannot be accurately fulfilled without wireless communication between a ground station and the spacecraft. In many applications, the satellite relies upon a wireless communication to send and receive electronic data to perform attitude and position corrections, diagnostic status checks, communication calculations and other functions. Without accurate wireless communication, proper satellite function is hindered and at times adversely effected.
Many modern spacecraft use potter horn systems for directing radiated radio signals. For direct radiating horn arrays, it is desirable that the horn elements have a high aperture efficiency to minimize the number of elements for a desired array gain. A potter horn, designed for low cross-polar level, typically has approximately 70% aperture efficiency.
Additionally, prior art horns may be used for reflector antennas producing multiple beams, commonly known as Multiple Beam Antennas (MBA). A typical coverage for an MBA is multiple uniform beam-cells, arranged in hexagonal grids that cover a certain area on the Earth""s surface. To simplify the beam forming network (BFN) structure, a single feed element is used to introduce a beam-cell. The cell spacing and the beam deviation factor of the reflector surface determines the maximum feed aperture size that can be used without mechanical interference of the feeds. Unfortunately, because of this, the required feed size is often too small. If a Potter or a conventional corrugated horn feed is used, the illumination taper on the reflector edge would be too low, creating a secondary beam with high sidelobes and increasing the interference level between neighbor cells reusing the frequency.
The disadvantages associated with these conventional radiating horn techniques have made it apparent that a new technique for a radiating horn is needed. The new technique should improve aperture efficiency while improving overall system performance. Additionally, the new technique should help reduce the number of elements required to support a Direct Radiating Array. The present invention is directed to these ends.
It is, therefore, an object of the invention to provide an improved and reliable multi-step circular horn system. Another object of the invention is to improve aperture efficiency while improving overall system performance.
In accordance with the objects of this invention, a multi-step circular horn system is provided. In one embodiment of the invention, a multi-step circular horn system may have several steps and may use more than one flared section based upon design considerations. In order to achieve high aperture efficiency, the aperture field distribution is close to uniform. For good cross-polar performance, the field distribution is circularly symmetric. Location and shape of the steps is determined by the wavelength of the signal being transmitted and the space constraints imposed by the antenna design. The step discontinuities generate desired modes of operation in the right proportion.
The present invention thus achieves an improved multi-step circular horn system. The present invention is advantageous in that it reduces the number of elements required to support a Direct Radiating Array and allow to improve the interference between beams in case of a Multi Beam Antenna.
Additional advantages and features of the present invention will become apparent from the description that follows, and may be realized by means of the instrumentalities and combinations particularly pointed out in the appended claims, taken in conjunction with the accompanying drawings.